Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 19806

GRB 160816A: Swift-XRT afterglow detection
2016-08-17T07:10:35Z (8 years ago)
Phil Evans at U of Leicester <>
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU),
S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A. D'Ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA), A.
Melandri (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of
the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 160816A (Racusin et al. GCN Circ. 19802),
collecting 1.6 ks of Photon Counting (PC) mode data between T0+25.2 ks
and T0+31.8 ks. 

An uncatalogued X-ray source is detected and is above the RASS limit,
and is therefore likely the GRB afterglow.  The position of this source
is RA, Dec=322.4108, +37.1324 which is equivalent to:

RA (J2000): 21:29:38.59
Dec(J2000): +37:07:56.6

with an uncertainty of 3.8 arcsec (radius, 90% confidence).  This
position is 3.8 arcmin from the Fermi/LAT position.  The light curve is
consistent with a constant source of mean count rate 7.8e-02 ct/sec. A
power-law fit gives an index of 1.5 (+1.8, -1.7).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.7 (+0.6, -0.3). The
best-fitting absorption column is  2.97 (+3.55, -0.16) x 10^21 cm^-2,
consistent with the Galactic value of 2.8 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 4.5 x 10^-11 (5.8 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.97 (+3.55, -0.16) x 10^21 cm^-2
Galactic foreground: 2.8 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.7 (+0.6, -0.3)

The results of the XRT-team automatic analysis of the likely afterglow
are at
The results of the full analysis of the XRT observations are available

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit